1. Field of the Invention
The present invention relates to an apparatus for dosing powdered or granulated additives in water works, in particular, but not exclusively, suitable for use in the field of swimming pools.
2. Description of the Prior Art
It is known that in water works the need often arises for the addition of water with antibacterial and/or generally disinfectant substances. Such substances, usually available in granular form and namely in powder, have to be dosed in a very precise and reliable way, in order to obtain the coverage required by the relevant hygienic regulations.
The problem is deeply felt in the case of swimming pools, chiefly public ones, where it is very difficult to guarantee wholly hygienic conditions, due to the organic pollution generated by swimmers, increased by the stagnant state of the water. On the other hand, the fulfilment of such conditions is fundamental to defend the swimmers"" health, and in this viewpoint the relevant regulations are particularly severe.
According to the method presently used in this field, the disinfectant powder, typically based on calcium hypochlorite, or in any case on chlorine, is preliminarily dissolved in a separate tank The additive-mixed water is then taken out with suitable dosing pumps and fed to the main works. Apparatuses which operate according to this method are described in U.S. Pat. Nos. 3,456,801 and 3,807,700. This method has some important drawbacks.
The first of them is that, being chlorine in general light-sensitive, when the additive-mixed water stays in the preliminary tank for long periods, which can last even some days, its disinfectant power decreases. Such decrease can be approximately about 50% in just a single week of light exposure. Then, to guarantee the fulfilment of the chlorine-coverage requirements, it is necessary to use much more substance than that theorically required, with a remarkable cost increase for higher product consumptions.
In the second place, dosing pumps which feed additive-mixed water to the main works are subject to frequent occlusions and failures, with consequent high costs for maintenance operations and/or replacements of worn out components. In fact, as the, product is chemically attacking, the widths of the flow sections have to be kept very small, this involving high flow speeds, with consequent increase of wearing phenomena. Such small sections are also easily clogged by calcium hypoclorite deposits.
A further drawback of the above described conventional method is that the workers having to carry out routine and unpredictable maintenance operations of the dosing system are forced to operate in troublesome conditions, since water with a high additive concentration is remarkably toxic.
Finally, in many cases the degree of chlorine coverage which can be obtained is unsatisfactory. As a matter of fact, when the system starts a very long transient condition occurs and several hours pass before the product has spread throughout the whole water volume of the swimming pool. And, in any case, even when the system operates in steady conditions, the above described preliminary dilution jeopardises a completely satisfactory result, i. e. a homogeneous product spreading.
The main object of the present invention is to provide an apparatus for dosing a powdered or granulated additive in a water works, namely a swimming pool, which allows a direct dilution of the additive in the water works, thus avoiding the above described drawbacks caused by the presence of preliminary dilution means.
A particular object of the present invention is to provide an apparatus of the above mentioned kind, which allows the accomplishment of an effective and homogeneous spreading of the product with a simple structure, which can be easily operated.
A further object of the invention is to provide an apparatus of the above mentioned kind, in which the possibility that ducts may be clogged is minimised and so the machine stops for maintenance operations and/or replacements of worn out components are reduced.
Said objects have been achieved with the apparatus for dosing powdered or granulated additives in water works according to the present invention, the main features of which are defined in the first of the appended claims.